Abstract

It had been previously established that ionizing irradiation either of eggs or 5th (final) instars of Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae) with 50–70 Gy would suppress the flight ability and reproduction of moths that emerged. A mean dose of 40 Gy was used to γ-irradiate larvae in oranges and in artificial diet in rearing jars to determine if the larvae reared on a synthetic diet would differ in radiotolerance from those reared in oranges. The mortality of irradiated larvae was low and very similar in rearing jars and oranges. A significantly larger number of eggs were produced by moths from 5th instars irradiated in rearing jars compared to that from oranges. However, the reduction in fecundity caused by irradiation was not significantly different for moths originating from both sources. Thus the fertility of the moths from larvae irradiated in oranges and in rearing jars from 4th and 5th instars was reduced by 64.6, 37.7 and 15.1%, respectively, compared to moths from non-irradiated control larvae. These differences were statistically significant and indicated that wild T. leucotreta were less radiotolerant than their artificially reared counterparts. Significantly fewer eggs were produced by moths from non-irradiated larvae in oranges than by moths from non-irradiated larvae in rearing jars. It is unknown whether the wild moths underperformed, or conversely, if performance of the insectary moths was enhanced by artificial rearing. Nonetheless, this aspect complements the experimental differences observed between the 2 larval sources in the experiment. The use of artificially reared T. leucotreta in research aimed at the eventual validation of ionizing radiation for the phytosanitary suppression of this pest in export citrus fruit is thus justified.